This invention relates to a shut-off and regulator device for controllable mechanisms intended for installation in pipelines.
Mutually compatible products of related kinds, such as oils, are pumped through a single pipeline for reasons of cost economy and reduction in space occupied. In order, in such instances, to prevent partial mixing between products when the products are changed, it is the usual procedure to evacuate the product already contained in the pipeline by means of a spherical, sleeve or cylinder scraper of elastic material scraping the internal wall of the pipe and effecting a seal there, which scraper, or as it is sometimes known a "go-devil", is subjected at one side to the influence of another pressurised medium (generally air) and is therefore displaced. The pipeline will lead, for example, from a storage dump comprising numerous vessels or tanks which are connected through tie-in pipes (product input) with the pipeline, to a distant tanktruck, ship-loading, process or mixing installation. To control the operation, a series of mechanisms are required, for example shut-off spools in the pipeline branches, a shut-off mechanism in the neighbourhood of the pipe tie-in points and filler mechanisms at the end of the pipeline in order to discharge a predetermined quantity of the product into the waiting tank, vessel or the like.
As far as tie-ins to pipelines which have a scraper facility are concerned, it is known to employ pipe connections to which the conventional mechanisms are attached by a flange or sleeve attachment. The entry cross sectional area is in this context annular or half-annular, with a minimum width, in order to prevent the scraper from jamming. Also known is a shut-off mechanism for a T-section pipeline branch, in the form of a manually-operated elbow valve whose core plug (which is always a nominal size smaller than the scraper line) extends up to the pipeline having the scraper facility and has a radius matching the internal radius of the pipe.
These known mechanisms to some extent suffer from major drawbacks. When running the scraper through these pipelines, residues are left behind at the cavities of the tie-in connections and mechanisms, which the scraper can not get at. These residues, left behind with each scraping operation, affect the quality of the product being pumped through the pipeline. For this reason, in practice very often the scraper method is discarded and each product is pumped through a separate line.
Commercially available valves, spools or gates, and other shut-off and regulating mechanisms, normally have no facility by which to avoid or indicate product mixing which has occurred as a consequence of defective seals. Accordingly, damage can be caused if, as a consequence of seals having become detached or defective, fractions of a product penetrate unperceived into one of the often numerous tie-in lines. To avoid this risk, very often two commercially available valves are connected in-line and in particular an itermediate section expanded across a third, smaller monitoring mechanism. However, in particular where remote-control is concerned, this measure turns out to be extremely expensive. Also, it occupies a large amount of space.
In the case of a mechanism which takes the form of a converted elbow valve, unfavourable flow characteristics are encountered because the nominal entry size must necessarily, for design reasons, be smaller than the nominal size of the pipeline for which the scraper is used. Because of the angled arrangement, this known kind of mechanism is very bulky. For remote-control, large and expensive diaphragm-type or piston-type drive arrangements are required. Moreover, the known mechanisms are not pressure-relieved and this means that corresponding spring arrangements have to be fitted in order to develop an opposing force. Where a pneumatic control is used, therefore, the air consumption is correspondingly high. A further drawback resides in the danger to the O-rings which are used as seals, more particularly in fact in the open position. The seals may be torn out by severe turbulence.
To shut off and regulate pipelines carrying liquid and/or gaseous products, already a whole range of mechanisms are known, a number in the form of standard designs. The conventional regulating and shut-off mechanisms of manually and remote-controlled kinds are relatively bulky. They normally employ glands or gaiters. The seats of these mechanisms are not pressure-relieved so that they are extremely susceptible to wear. This applies in particular to mechanisms designed to pass scrapers.
Again, in the case of mechanisms used in filling applications, there is a whole range of known designs all of which have the drawback that the scraper can not be operated right up to the exit and frequently, too, remote-control is not possible.